FIG. 7 is a sectional view showing an example of a conventional fuel injection valve.
As shown in FIG. 7, a conventional fuel injection valve 1 is configured such that a valve body 8 serving as a movable element that forms a valve mechanism is composed of an armature 9 and a valve portion 11; the valve body 8 is pressed to a valve seat 10 by a spring 13 when the valve is closed; a magnetic field generated by a coil 2 generates magnetic suction force that suctions the armature 9 to a core 3 side when an electrode terminal 7 is energized; and thus, the valve body 8 is moved to the core 3 side to generate a gap between the valve portion 11 and the valve seat 10, that is, the valve is opened and fuel flows.
Furthermore, in the conventional fuel injection valve 1 shown in FIG. 7, a magnetic path include: the core 3, the armature 9, a holder 4, a housing 5, and a cap 6. At this time, the coil 2 is accommodated in the housing 5 and the cap 6 is welded and fixed to the housing 5 in the form covering the coil 2 in a lid shape. The cap 6 is press-fitted onto the holder 4 and then welded and fixed thereto, and comes into contact with the housing 5 at a tapered surface to stably secure a contact area with the housing 5. At this time, the housing 5 and the holder 4 are set to have a gap therebetween from a standpoint of absorbing axial deviation; and in order to compensate magnetic loss due to the gap, the configuration is made such that the facing length Li of the holder 4 and the housing 5 is lengthened. (See Patent Document 1.)
In addition, FIG. 8 shows other conventional example; and in a conventional fuel injection valve 1 shown in FIG. 8, a core 3 and a holder 4 are integrated. Then, as shown in FIG. 9 in which a part A of FIG. 8 is enlarged and is shown, a thinned portion 15 is provided at a part of the holder 4 and magnetic leakage, which does not pass through a suction facing surface but passes through this part of the holder 4, is limited to improve magnetic efficiency than that of the fuel injection valve of FIG. 7, (See Patent Document 2.)